Parents of pre-teens worry about what the teenage years will bring, joke about the probable stresses ahead, but quietly assume that, somehow, they and their children will muddle through.

Usually, they're right.

Fantasies of being talked of in hushed tones as the parent of the pupil who won 600 points and a scholarship to Trinity may not come true, of course. But lurid fears that our child will fall prey to the dangers of sex 'n' drugs (forget the rock 'n roll) usually prove exaggerated too.

But not all the time. What if your teenage child goes off the rails, falls into bad company, starts failing at school, becomes addicted to drink and/or other drugs, goes AWOL, doesn't come home at night, does come home - in a police car, becomes pregnant at 14 or 15?

What if your previously sweet subteen starts behaving like the lead in a bad 1950s teen-rebel movie, and won't listen to a thing you say?

A percentage, but usually a surprisingly small one, of all teenagers always did and still do "go off the rails" in these years. Whether their extremely difficult behaviour is triggered by factors that have been lurking since early childhood or by a combination of external events and internal insecurities, the result is extremely stressful for their families.

How do they cope? How do parents who don't know whether their child will still be in school even to sit the Leaving Cert cope with tackling their child's problems - and put up with parents whose biggest problem is whether to get grinds to help their child get those 500-plus points? How can they bear listening to parents whose big worry is whether or not to allow their 14-year-old go to the junior disco once a term, when their child has a tantrum and goes missing overnight because they want him to stay home on school nights? How do they cope when it seems that everybody else's teenager sticks to the straight and narrow?

Maire, a mother of three whose youngest child was causing major hassle all around him, remembers meeting a friend in a shop one day who asked casually "how are the kids?" Maire burst into tears, much to her friend's alarm. But because she and her husband - solid citizens with a track record of successful parenthood - are open and honest about their situation, they've discovered that quite a few families have problems just like theirs.

"The biggest lesson I've learned is that many parents are going through this and don't speak out. There's a massive reluctance to talk about this kind of problem," Maire says.

"I do believe that there are many more people with bigger problems than ever say it aloud. We learn more, hear more, because we're candid - and find other parents saying `thank God I'm not the only one'. "Parents do feel that a child's bad behaviour is their fault, their failure, see it as a reflection on themselves, but it's not necessarily - there's a lot of other influences on kids."

Margaret Lamont, chairperson of Parentline, confirms that there are plenty of "problem kids" out there. "We find that a lot of big problems start when a child is 14 or 15, when children have more money of their own, look older, can - for example - get into pubs. The goalposts have changed, and many children have no idea of authority any more." Factor X, of course, is the widespread, easy availability of drugs (including alcohol), which, as Lamont says "make everything worse".

Many teens with problems will get therapy, and parents may draw advice from this source. But otherwise, where can parents turn to for help in coping?

Many, probably most, parents talk with each other about their children from the time they're born, comparing notes, sharing experiences and drawing a lot of support from each other as they do so. But many parents instinctively clam up when the problems become serious.

Lamont agrees that parents do care what other people think and "tell us stuff they would hate their neighbours to know". But like senior clinical psychologist Marie Murray, she believes there are potential problems in revealing too much to too many people.

For one thing, other parents may be sympathetic to your problems - but might try to keep their teenagers away from your child, if your confidence has the effect of giving your child a "bad name". And there's the issue of how much of your teenager's problems it's fair to talk about - after all, you wouldn't be thrilled if they revealed some of your secrets in public.

Murray says there are dangers in speaking too soon, too much or too specifically. For one thing, a phase of trouble may turn out to be short-lived and speaking about it "may unnecessarily draw attention to the teenager". And if the problem will have "long-term ramifications for the teenager when they resolve their problem - e.g., serious drug or alcohol abuse - the source of help and reassurance is more appropriately a professional one."

Parents should also keep in mind what lies ahead for a teenager who has "reformed": "If they continue to be treated warily or antagonistically, they may revert back to the logic of `if that's what they think of me, I may as well be doing it'."

She also advises parents to consider their child's right to privacy. "It is not suggested that parents make false claims or remain overly `closed' or unable to tell other parents that `X is going through a difficult patch at present'. But young people do have the right to make their mistakes within the family context and to have them resolved with the support of the family."

Many children are loyal to their parents in speaking about them, Murray adds, and "to find their behaviour is being liberally discussed would evoke a sense of betrayal".

Both Murray and Lamont agree, however, that sharing a problem with a trusted friend, someone on to whom you can off-load your feelings, or bounce ideas off, may be necessary to help adults through a difficult time. But whether you're disclosing your problems to friends or professionals, the important thing is that you do trust them to keep your confidences.

Parentline is a good resource: it has a drop-in support group based in Eustace Street in Dublin, which parents in crisis can drop into and out of, and also organises 10-week support groups, where most of the parents would be coping with serious problems. In a parent support group, confidentiality is usually ensured because, as Lamont says, "after a few weeks, parents realise they're all in the same boat once they've bared their souls."

And as for parents who don't have these problems - remember that the first rule of parenthood is "Don't be smug". As Lamont says: "Parenting is a hard act, and most of it is trial and error." There is good and bad parenting, but most parents do their best.

"Some of us are lucky, and some are not."

Parentline's phone number is (01) 873 3500